I just want to make sure that everyone understands that my own conclusions are that there are very questionable benefits to this approach... while siliconizing the bag results in a nice tight bag and bellows, longevity is questionable, and toxicity and reed degradation may be issues.

Hi Harlow, all...

First - sorry to nitpick but this has been bugging me for months and I just can't help myself... It's silicone, i.e. think cosmetic surgery, not siliCON which is a semiconducting metal used in electronic components. Possibly 3M is misspelling it in their product name but that would just be daft.

Andreas Rogge used to use a silicone-based clear sealant inside his bags; I don't know if he still does.

I don't think there is a real toxicity issue, insofar as nothing from inside the bag should be finding its way into your body. The toxic ingredient in these sealants is mostly the fungicide, which as previously mentioned can be avoided by choosing a product without it. You guys use caulking in your homes, don't you? More of a worry in the kitchen and bathroom than in the bag, and the stuff is sold for use in kitchens... some types even for aquaria. Similarly I fail to see a problem with the reeds, at least after the initial cure period where acetic acid (i.e. vinegar) is off-gassed. Longevity for bags seems fine, at least based on anecdotal reports and my own previous experience with Rogge bags.

Better to obtain proper leather; chrome tanned elk hide that needs minimal or no seasoning, or quality upholstory leather plus beeswax + oil (neatsfoot or olive per preferance, rosin) seasoning; or go with an airtight synthetic like Naugahyde or the more durable/costly and less stretchy Hypalon. And, use a bag cover.

Obtaining the proper leather seems difficult right now in the US. Several current sources have been suggested, and they have been discouragingly unresponsive, at least to my queries. Leather Factory / Tandy does not usually have the "right" stuff, though occasionally something suitable is in stock.

Perhaps there is an international bagpipe leather cartel. How do I join?

I learned a lot in the process.

Finding the "right stuff" in the pipes business often takes a lot of digging. I see little advantage, and much to dislike, in bag covers, but then again I don't tend to sweat profusely when playing pipes (preferring lighter reeds). For those who do I can see a potential problem with suede-side-out leather bags. Bonding/delamination can be at least as big a problem with wax/oil-based treatments as with silicone - in fact I would say greater, as the silicone doesn't tend to creep with time and temperature. Most attempts at oil/wax treatments which I have encountered have yielded results that I found unsatisfactory (I refer here to the end result of _other_ peoples' treatments, including experienced makers), but that doesn't mean that it is not possible to get good results.

The "good" results I recall encountering are (not necessarily in this order, and in my own opinion):

(formerly) Dominion Leather as used by L&M, which is chrome-tanned and then treated with a non-oily/non-waxy polymer coating or some kind (proprietary);
Rogge bags with some silicone-based coating on the inside (possibly applied after stitching, it was not really obvious);
MacHarg bags, which were once I believe made with Dominion Leather (same coating) but are now made with something else and rivited;
Chrome-tanned leather coated with Evo-stick brand contact adhesive thinned 1:1 with thinner/solvent (the old formula, no longer available).
I have also used bags from another fellow in the North of Ireland which were reasonably airtight without further seasoning, but it is not apparent whether the leather has a coating; these are perhaps not quite as airtight as the varieties above.

I have heard of good results achieved with pour-in thin latex, but it is important to remove all stocks etc. before adding any sealant, and the latex will stick to itself unless is is powdered/chalked afterwards, which is probably bad for the reeds. This last treatment is one that has received bad press online before, I cannot personally recommend it.

I don't think any of these approaches are really sufficient for bellows though, since the nature of bellows is such that there are tight folds and places where the leather is constantly rubbing together in service. That would tend to degrade any coating over time. The answer for bellows seems either fairly thick, airtight leather from the start, or a 2-ply leather gusset (with a glue layer in between that both seals the leather and forms an additional barrier). I think the latter is more common.

I've never been able to reach Dominion Leather. If it still exists, does anyone have contact information? I believe they were in Canada.

Americraft Leather was suggested in a PM, but so far I have had poor luck getting them to answer their phone or return a call. If I can get through to them, it was suggested that I send a sample of something like what L&M uses and see if they can match it. At least one established US pipemaker uses them.

I am looking at a bit of L&M bag remnant now and if they are using some sort of sealant, it is not particularly obvious. Perhaps it is in how the leather is tanned or treated? You say that is proprietary?

I've made two bellows now using the two layer glued gusset approach you describe. What worries me again is delamination. I actually had that happen rather quickly on the first of the two bellows, using a glue called "Leather Bond". The second two-walled gusset I made used a glue called "Barge" cement which is a contact cement similar (perhaps?) to the Evo-Stick that you mention. It can be thinned. I bonded thin pigskin glove leather to nice upholstery leather, nap to nap. However, I have a sinking feeling that the bond will fail before the bellows does.

I've never been able to reach Dominion Leather. If it still exists, does anyone have contact information? I believe they were in Canada.

Americraft Leather was suggested in a PM, but so far I have had poor luck getting them to answer their phone or return a call. If I can get through to them, it was suggested that I send a sample of something like what L&M uses and see if they can match it. At least one established US pipemaker uses them.

I am looking at a bit of L&M bag remnant now and if they are using some sort of sealant, it is not particularly obvious. Perhaps it is in how the leather is tanned or treated? You say that is proprietary?

Dominion is long gone; the talk is that L&M hired a former employee and was doing the coating themselves, but I have doubts about that as L&M have themselves changed leather a couple of times since. The L&M stuff does seem to have a very thin coating, which as you say is not obvious; that seems to be a good sign as it does not easily delaminate from the leather. Everything reliable which I've heard indicates that this is indeed a proprietary coating, rather than something in the tanning process.

I've made two bellows now using the two layer glued gusset approach you describe. What worries me again is delamination. I actually had that happen rather quickly on the first of the two bellows, using a glue called "Leather Bond". The second two-walled gusset I made used a glue called "Barge" cement which is a contact cement similar (perhaps?) to the Evo-Stick that you mention. It can be thinned. I bonded thin pigskin glove leather to nice upholstery leather, nap to nap. However, I have a sinking feeling that the bond will fail before the bellows does.

I think 'Barge' is similar to the Evo-stick; however Evo-stick recently removed toluene from their formulation, using naptha now instead, which seems to have substantially reduced the bond strength. If Barge is using toluene etc. it should be fine. For dual-layer gussets I think delamination is unlikely - highly unlikely in my experience with the "old formula Evo-stick", as the bond is much stronger than glove leather (i.e. the leather will pull apart before the cement yields, even after a long time). But don't thin the glue in this case, use it full strength and don't skimp much. If you use the cement as a sealer, on the other hand, thinning it will aid penetration into the leather and help reduce any tendancy for the treated leather to be tacky and/or stick to itself later on. In my experience delamination has only occurred when the initial leather bond was poor due to insufficient coverage and/or too little cement - speaking about a time period of 6 or 7 years plus, without even slight signs of delamination.

Upholstery leathers can be funny - some of it is nice but some of the thinner "finer" grades can be rather porous and/or elastic which isn't really what you want, especially if one layer is glove leather or thin calf, since then only the glue will be preventing stretch. I've had good results with a rather inelastic yet thin leather, I think it was designed for dress shoes (not patent but similar in finish), when bonding to the softer finish leathers in 2-ply for tacked bellows. (I use the shiny "shoe" leather on the inside in this case.) For stitched bellows I think you need a different combo, something that will hold stitches without tearing yet with enough elasticity to allow the gusset to adopt the proper shape.

Hi Bill. I can confirm that the "Barge" brand still contains toluene. It is nasty stuff to work with, and I only do it outside with a mask. But it works great. It is a bit difficult to acquire in the US, because of the toluene component. I had to register as a business buyer with Leather Factory to get them to sell it to me. However one done, it can be bought from that source, and you get a significant discount.

Basically I constructed my double gusset bellows as you suggested, not thinning the 'Barge' cement at all. David Daye suggested that the barge cement was strong enough to hold the gusett lapped end alone, but I sew it anyway. His argument was the same as yours, that unthinned "Barge" was as strong as, or stronger than the leather, and that sewing only introduced potential leaks. For what it's worth, "Barge" has a thinner product usually sold alongside.

The leather I am currently using (you can go to the beginning of this thread to view the bag or to my blog listed below and scroll down a bit) is the kind of upholstery leather used for couches, and is quite thick, though not as thick as a chap leather. It is almost airtight, and completely airtight if seasoned. It is not inexpensive. Leather Factory had some great vegetable tanned Buffalo hide that seemed perfect recently (very airtight), but it was a sale item and sold quicker than I could return to get some.

The one stitched bellows I've made to date, used the same thick upholstery leather, with no double gusset, and only seasoning. Surprisingly, it works fine. It also held the stitches well. It was made according to DMQ's tutorial, and included a 'welt'.

I did this experimental silicone treatment bag and bellows in 2008. It is now almost 2016. Bag and bellows remain supple and airtight, and are in use almost on a very regular basis throughout. No problems with reed degradation observed. My personal conclusion is that GE Silicone works just fine as a bag or bellows air sealant treatment.